1. Field of the Invention
The present invention relates to a flat display device, and more particularly, to a flat display device having an anti-peeping function.
2. Description of the Prior Art
Although wide viewing angle technology has been an inexorable trend for enhancing the contrast of liquid a crystal display (LCD), it is often desirable that a viewing angle be restricted in certain applications of LCDs, so that users can only see the image within a particular field of view. For instance, when a user is operating an automated teller machine (ATM), using a laptop computer in public while handling personal documents or handling an industrial computer, under considerations of safety and privacy, a flat display device with a narrow viewing angle or one that can provide an anti-peeping function is required. In this way, a clear view of an image or information would be limited to those users who are looking squarely at the display device, instead of other people standing alongside.
Current viewing angle narrowing technology or anti-peeping technology attaches another film having an anti-peeping function to the surface of the wide viewing angle flat display device. For instance, in U.S. Pat. No. 6,398,370, Chiu, et al. disclose a polymer film having an anti-peeping function. Utilizing the light-blocking physical property of the polymer film enables the users to view the displayed image of the flat display device within a fixed field of view, while others outside the field of view cannot view the displayed image. The shortcomings, however, of using the polymer film are that the additional polymer film of a certain thickness adhered to the surface of the display device is expensive, and thus increases the cost and thickness of the flat display device.